Differentiation of monocyte-derived dendritic cells on endothelial cells as feeding layer

The innate and adaptive immune responses are dependent on the migration of leukocytes across endothelial cells. Dendritic cells (DCs) play an important role in the initiation of cellular immune responses during their migration from tissues into the lymph nodes where they interact with endothelial cells of lymphatic vessels. We investigated the effects of surface-adherent and non-activated endothelial cells on phenotypic and functional characteristics of dendritic cells. Immature dendritic cells were generated from the isolation of peripheral blood mononuclear cells and their subsequent culture in DC-RPMI 1640 medium containing 10% FCS, interleukin-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF) for five days. On day five, a maturation factor (composed of monocyte-conditioned medium, tumor necrosis factor-α (TNF-α) and poly I:C) was added to the RPMI medium where immature DCs were co-cultured with endothelial cell monolayer for 24 h. The maturation of harvested DCs on day seven was evaluated via flow cytometry, a beta-counter and an ELISA kit. This study showed that the endothelial cells interact with dendritic cells generated from peripheral blood monocytes via cell-to-cell interaction. This interaction inhibits the maturation of DCs via decrease in the expression of CD83, CD86, CD80, HLA-DR and up-regulation of CD14. The interaction also inhibits the stimulation of T-lymphocytes resulting in a decrease in their proliferation. According to the findings of this study, it could be concluded that the endothelial cells can act as a potent regulator for DCs differentiation and function at the encounter made between them during the migration of DCs from tissues to lymph nodes.